Technical Field
The present invention relates to a stator for a rotating electric machine mounted in a vehicle or the like and used as an electrical motor or an alternator.
Related Art
A rotating electric machine to be mounted in a vehicle is well-known that includes a rotor, a stator core having a plurality of slots radially opposing the rotor and arranged in a circumferential direction of the core, and a stator having a stator winding wound in the slots of the stator core.
A known stator winding wound around the stator core, as disclosed in Japanese Patent No. 4450125, is a segmented stator winding formed by connecting terminals of a plurality of U-shaped conductor segments. Such a stator winding is formed by inserting a pair of straight portions of each U-shaped conductor segment into different slots from one of axial ends of the stator core, bending a pair of open end portions of the conductor segment protruding from the other axial end of the stator core in opposite circumferential directions to form a pair of angled portions, and then joining, e.g., welding, the angled portions of different conductor segments together to form a joined connection. Each U-shaped conductor segment includes a conductor and an insulative coating covering a peripheral surface of the conductor.
When, as above, the open end portions of each U-shaped conductor segment protruding from the other axial end of the stator core are bent in opposite circumferential directions with predetermined (constant) pressure to form the angled portions of the U-shaped conductor segment of the segmented stator winding, the U-shaped conductor segment will become in contact with corners where an axial end face of the stator core and inner walls of slots in which the U-shaped conductor segment is inserted meet. The insulative coating covering the peripheral surface of the conductor segment is prone to be damaged or collapsed, which may lead to insulation failure of the stator winding.
In addition, the stator winding produces heat through energization to become hot. Elevated temperature of the stator winding may cause the insulative coating of each U-shaped conductor segment to thermally expand. The insulative coatings of slot-received portions of the U-shaped conductor segment are prone to be damaged or collapsed within the slots of the stator core under stress due to a difference in the coefficient of thermal expansion between the insulative coating and the conductor of the U-shaped conductor segment. This also leads to insulation failure of the stator winding.
In consideration of the foregoing, exemplary embodiments of the present invention are directed to providing a stator for a rotating electric machine capable of preventing insulation failure of a stator winding from occurring during bending of conductor segments to form the stator winding or in high temperature environments, thereby ensuring good insulating properties.